Thiazine dimer



Patented Apr. 20, 1948 UNITED STAT THIAZINE DIMER Frank Swedish, Jr., Rothschild, Wis., assignor to I V The B. F. Goodrich Company, New York, N. Y., a corporation of New York No Drawing. Application August 7, 1946, Serial No. 688,960

7 Claims. 1

This invention relates to new compositions of matter and pertains specifically to the dimer of 2 mercapto-4,6,6-trimethylthiazine and its metal salts.

I have discovered that the dimer of Z-mercapto- 4,6,6-trimethylthiazine can be prepared by treating 2-mercapto-4,6,6-trimethylthiazine or 2-mercapto-4-hydroxy-4,6,6 trimethyldihydrothiazine (which may be regarded as the hydrate of the mercapto trimethylthiazine) with an aqueous solution of the dehydrating mineralacid of a concentration hereinafter set forth, and then heating the reaction mixture. The reaction may be represented in the following manner:

(CHa)2OCH=COH Mineral I I 2 S -C=N S -C==N Acid I SH heat SH 2 (M. W. 173) (M. W. 346) capto-4 hydroxy-4,6,6 trimethyldihydrothiazine can be prepared by reacting dithiocarbamic acid with mesityl oxide, preferably by adding a salt of dithiocarbamic acid to a mixture of mesityl oxide with an aqueous solution of hydrochloric acid at a temperature of about to 40 C. and

i then heating the reaction mixture, the dihydrothiazine, which is an intermediate in the preparation of the thiazine, resulting if the product is insufiiciently heated. The preparation of these compounds is more fully described in the copending application of Jacob Eden Jansen Sr. No. 557,- 384, filed October 5, 1944, particularly in Examples I to I11 thereof.

The preferred procedure of this invention is to treat 2-mercapto-4,6,6,-trimethylthiazine or 2- I mercapto-4-hydroxy-4,6,6 trimethyldihydrothiazine, with an aqueous solution of sulfuric acid containing not less than 50% sulfuric acid by weight but not more than 80% by weight and then heat the reaction mixture to a temperature not in excess of C. A more detailed description'of the preparation of the-dimer is given in the following example in which the parts are by weight. I

Example I 500 parts of 65% sulfuric acid' were added to 430 parts of 2-mercapto-4,6,6-trimethy1thiazine in a reaction vessel with stirring. There was an immediate temperature rise to about 50 C. and the slurry changed to a red color. The reaction mixture was then heated to about '75 C. for 30 minutes, and the slurry turned to a tan colored paste. 3,000 parts of water were added to the paste with stirring. The dimer settled out of the aqueous diluent as a finely-divided, yellow crystalline solid. The product was filtered, washed free of acidand dried at room temperature. 411 parts (96% yield) of the dried dimer,

which had a melting point of to 200 C., were thus obtained. When purified by recrystallization the dimer was found to possess a melting point of 206 C. and a molecular weight of 342. The thiazine originally used, however, had a melting point of 97 C. and a molecular weight of 1'73, thus showing that dimerization had occurred.

A chemical analysis of the dimer showed the following composition as compared to composition calculated from the theoretical formula.

ByAnalysis Calculated I Per cent Per cent Carbon 48. 52 .50 6.44 6.40 8.09 8.09 37.02 37. 01

When the example was repeated using 2-mercapto-4-hydroxy 4,6,6 trimethyldihydrothiazine in. place of 2-mercapto-4,6,6-trimethylthiazine,

a good yield of the same product, melting at 206 C. was likewise obtained.

Various other modifications in the procedure of the example may also be effected while still obtaining the thiazine dimer in good yield. Thus, although the use of sulfuric acid is preferred, such other dehydrating mineral acids as hydrochloric acid and phosphoric acid may also be used. The concentration of the acid,. however, is critical trirnethylthiazine' but"; in h w T eka me e water and are eet m uins nu es; piypyadd:

. droxide for each mol'ecular edui .to an aqueous solutio" and must be that which is equivalent to aqueous sulfuric acid containing 50 to 80% sulfuric acid by weight, for, if the concentration is above 80% there are obtained products other than the dimer,

while concentrations of less than 50% convert 5 little or none of the thiazine to the dimer. I have found that concentration or sulfuric acid of about 60% to about 75% give the most satisfactory results.

The acid is recovered quantitatively from the and the pro ct ad the Same p p aqueous diluent and appears to act as acatalyst for the dimeriaation of the thiazi'ne. "j Theamount of acid re'quired'to bring about'the dimerization is not critical and can be varied, it being pre- Escample III ferred to have ufii i nt aqueous acid Qntq thG same amounts of reactants and diluents as to produce a slurry that can be readily stirred to insure not only good Contact betweerithabid nd the thiazine but also t' ivc good he'attrtnsa p'jowder' liadafmelting point of 205-207 C. and

fer throughout the reactionmi'iitiire. Thisjf'is above except that 150 parts of zinc chloride was used in place of the lead nitrate. The zinc salt o f the dimer, which was a white finely-divided accomplished in general by the use of a greater 2 W b fii i i iii y of slurry is notcritialasa 'ractioni'cbnditiorflbut the slurry shouldbe"heat'ed for a-timef'sumeient to give good conversions, which can'r'e'adilyfbe v x It will be understood that other water insoluble lmetafs'alt's of the dimer can be formed in a simi- "lar-manner by substituting salts of such metals as'iron; cadmium, copper, mercury, magnesium, manganese, calcium, strontium, aluminum and others for the lead and zinc salts in the above *eire r i ns ,The" thiazirie tie-r; anditsmetal saltsj particularly those ofdivalentnietalsfare'eiicellent ac'oeldetermined for anyiven "set of conditions, and so F 0f vlllcanizatmn rubbillnatllmlimd the time of heatingshould be considered as an economic factorjin the selection" of" reaction equipment. The temperatur to wh'iclithe thiazine-acid slurry is heated the slurry should not bei heated be lates not only to t e" dimer 1 2 um ceing the dimerto a heated; g 'lutioncon- ,taining two molecular equivalents oflall ialfh'yelnt offdii'tier.

'Otherfmetal salts are general y and are quite eaeu prep jred y edema-ant que:

one solution of a water solublesjalt ofth metal "r aa'airaiiae ai s a of the dimer whereupon a eeenieneai reaen n eeours and the insoluble' metal'salt of'th'"dimer duced' 'in natural and synthet" dimeritself as well as its zinc "and lead saltsf-"I'he synthetic; f Among thefrubberswith which these eoi'r polund'smay be usedare altvar etie's of naturubber; 'such jas jc'aoiit'chouc, ffbalataifl gutta rchaiil l' f fixgirejclaimed rubber,"artificial-rubber r e, inthyl -acrylate, methyrmet a e jand other coj'p'olyrnerizable morromers. The dimer and its metal salts may be adged'to the rubber on a roll f mill or in an internal mixer or by ahy'other suit- "able method by which compounding ingredients 45 are incorporated into rubber compositions. The J presence pi other compoundingingredients such dinary 'p igrnents, fillers? antie avenodeleteritape-teeter my ratingfpower of e the effect pro- "r'ubber by the prec itates and is recovered by filtration in sub ifqnpwmgtmbbgrlgompositions" mwhichthparts stantially theoretical yields.

i entire mass thickenedtoapastel A'sma'llamount of dilute hydrochloric acid was'added t'oithe'paste are eyes-grit'weiepreeared.

The following examples illustrate the prepara- V I tion of metal salts of the dimer. Natural Rubber y thetic Rubber gg f" Example II V 60 larts The lead salt of the dimer was prepared by (118- g bC --r" 2 figs. t sri of solving 260 parts of the dimer in 500 parts of hot .i 5w ,;1 v agx and tap water to which 66 parts of sodium hydroxide m fig had been added. Theresulting solution"w|as de- '1' a 5 i3 7 canted to removea trace of ioreignniaterial. To l fi oben; L x the aqueous So ut 0f i E P I T Offthe .II: ZGIGCEXSHIDIG "Benz thiacyl-2disillfiile, 2'25 dimer, there adde'd with stirrin'g2'i3 parts Je gg g lgg e .1 E of lead nitrate dissolvedinf5llllpartsofiwater. Zine sign er b'i'eir'f A heavy precipitate immediately "formed; and the Examine E resettlement,am n qt a o m sitiion's at 280; F: for various lengths of time, the

' resulting vulcanizates hadfthe physical proper- ;ties as set forth: in the following table; in-which 5 T is; the ultimate'tensile"strength in pounds per square inch and E is the ultimate elongation in percent.

6 to aqueous sulfuric acid containing from about 50 to about 80% sulfuric acid by weight.

Table I Synthetic Rubber: GR-S Natural Rubber Time of Vulcenization, minutes Ex. A Ex. B Ex. 0 Ex. D Ex. E

T E '1 E T E T E '1 E The above data indicates that the dimer and its salts are more efiicient accelerators than such commonly used accelerators of vulcanization as Z-mercaptobenzothiazole and benzothiazyl-Z disulfide.

While I have herein described specific methods of preparing the compounds of my invention, I do not desire nor intend to limit myself solely thereto, for, as hitherto stated, the precise proportions of the materials utilized may be varied and other materials having equivalent chemical properties may be employed, if desired, without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1, The method of preparing the dimer of 2- mercapto-4,6,6-trlmethy1thiazine which comprises heating a thiazine selected from the class consisting of 2-mercapto-4,6,6-trimethylthiazine and 2-mercapto-4-hydroxy-4,6,G-trimethyldihydrothiazine in the presence of an aqueous solution of a dehydrating mineral acid at a temperature not in excess of 90 0., the concentration of the mineral acid being that which is equivalent 2. The method of preparing the dimer of 2- mercapto 4,6,6 trimethylthiazine which comprises heating said thiazine in the presence of an aqueous sulfuric acid solution of a concentration of about to about 80% by Weight at a temperature not in excess of 90 C.

3. The method of preparing the dimer of 2- mercapto 4,6,6 trimethylthiazine which comprises heating said thiazine in the presence of an aqueous solution of sulfuric acid of a concentration of about at a temperature of '70 to C.

4. A compound selected from the group consisting of the dimer of 2-mercapto-4,6,6-trimethylthiazine and. the metal salts thereof.

5. The dimer of 2-mercapto-4,6,6-trimethylthiazine.

6. The lead salt of the dimer of Z-mercapto- 4,6,6-trimethylthiazine.

'l. The zinc salt of the dimer of Z-mercapto- 4,6,6-trimethy1thiazine.

FRANK SWEDISH, JR. 

